In this effect the behavior of a
spectator is predicted not once, but three times over. Your spectator
examines a blank faced deck of cards. On six of the cards you have drawn
symbols - two cards with a circle, two with a square and two with a
cross.

She observes you position three different symbols cards
at various locations inside the pack of blank cards. The deck is then
turned face down and she is asked to position the matching three symbol
cards face down at various places in the deck. She is given complete
freedom where she places her three cards.

This completed, you
explain that you are not now going to pick up the deck and do a lot of
jiggery pokery or sleight of hand with it, because this is not a trick.
We like to think our actions are under our control, or at least maybe
just random. But actually our behavior is curiously predictable.

You
simply turn the deck face up and spread the cards across the table.
Each time she placed a symbol right next to one of yours. But not only
that, astonishingly, each of the pairs match precisely.

This
version of the card matching effect has a number of points to recommend
it. Three matches make a big effect, the ESP symbols give a strong
mentalism feel, you are completely clean at the end, there is no
tell-tale evidence that the effect was anything other than entirely
genuine, there are no gaffs of any type, it's easy to do, and the only
requirements are a blank deck and a marker pen to draw on the symbols.